Generating Cutting Forms Along Current Flow Direction In A Circuit Layout

ABSTRACT

Metal is deleted from portions of metal wires in an integrated circuit layout, based upon a width of the metal wires. Preliminary cutting forms having a length and a width are inserted with a first orientation in the portions of metal wire. It is determined if the width of each of the preliminary cutting forms is parallel to a width of the metal wire portions where the preliminary cutting forms are inserted. If the preliminary cutting forms have width parallel to the width of the metal wire portion, the preliminary cutting forms become part of a cutting form final layout. Cutting forms not having widths parallel to the width of the metal wire portions are removed. Cutting forms at different orientations are then inserted where the prior cutting forms were removed from and the process repeats until all portions of the metal wire have cutting forms inserted parallel to the current flow direction.

FIELD OF DISCLOSURE

The embodiments disclosed herein relate generally to manufacturingtechnologies for electronic circuits and, more specifically, to a methodand apparatus for generating cutting forms in a circuit layout.

BACKGROUND

In integrated circuit (IC) layout, wide wires (for example, wider thanten microns) are designed for carrying large electrical current. Forexample, power buses are usually wide metal wires formed from copper oraluminum to obtain low resistance. However, in the course ofmanufacturing, a chemical mechanical polishing (CMP) process toplanarize the metal layers and other portions of the circuit oftenproduce concave “dishing” in the metal surface, where dishing is moresevere where the metal wire is wider. That is, when polished, the centerpart of the surface of the embedded metal wire forms a “dish-like”profile where the thickness of the metal wiring is reduced at thecenter. Furthermore, CMP heavily depends on the metal width and density.Metal dishing is more serious for larger line widths and where portionsof an integrated circuit have a high area fraction containingmetallization.

To remedy this problem, shapes (“cutting forms”) in the form of polygons(e.g., rectangular slots) are placed into metal wires during designlayout to indicate where to cut holes within the metal wire pattern. Theholes lead to a reduction of the effective metal width and area densityin any local region, breaking up the larger expanse of the metal wirewidth, and reducing dishing effects, thus limiting the thinning of themetal wire. When adding the cutting forms in the shape of elongatedslots, it is highly desirable to place the long dimension of the cuttingforms parallel to the direction of electrical current flow. This is doneto facilitate the current flow and therefore reduce the effect ofelectromigration, a cause of increased path resistance, conductivitydegradation and failure.

Conventionally, cutting forms are added into a layout manually. This canbe a time consuming process. Another method may include inserting therectangles into wide metals using a conventional programmed script. Alimitation of this method is that the added rectangles may not always belaid out parallel with the current flow direction, particularly when themetal wire turns a corner and the direction of current flow changes.Consequently, manual intervention and modification is involved tocorrect the orientation of added rectangular slots.

There is a need, then, for an automated method of laying out cuttingforms correctly oriented along the current flow direction of the metalwire.

SUMMARY

A method of inserting cutting forms in metal wires in a circuit layoutis disclosed. The method identifies wires wide enough to determine whento insert cutting forms, i.e., the removal of metal sections in stripsfrom portions of wide metal wire, where the cutting form strips areoriented with the long direction parallel to the direction of currentflow.

A method for generating a cutting form layout including cutting formsfor deleting metal along a current flow direction in an integratedcircuit layout includes identifying a metal wire in the integratedcircuit layout to receive the cutting forms. The metal wire includes atleast one metal wire portion having a portion length edge and portionwidth edge. A first group of preliminary cutting forms with a firstorientation are inserted within the at least one portion of the metalwire. Each of the first group of preliminary cutting forms has a widthedge, and a length edge longer than the width edge. It is determined ifthe width edge of each of the first group of preliminary cutting formsis substantially parallel to the width edge of a corresponding portionin which the group of preliminary cutting forms are inserted. Any of thefirst group of preliminary cutting forms not having the width edgesubstantially parallel to the width edge of the corresponding metal wireportion are removed. The first group of preliminary cutting forms havingwidth edges determined as substantially parallel to the width edge ofthe corresponding metal wire portion are defined as final cutting forms.

A computer program product for generating cutting forms for deletingmetal along a current flow direction in an integrated circuit layout,includes a computer-readable medium comprising code for causing acomputer to identify a metal wire in the integrated circuit layout toreceive the cutting forms. The metal wire has at least one metal wireportion having a portion length edge and portion width edge The mediumalso includes code for causing a computer to insert with a firstorientation preliminary cutting forms within the at least one portion ofthe metal wire. Each of the plurality of preliminary cutting forms has awidth edge, and a length edge longer than the width edge. The mediumfurther includes code for causing a computer to determine if the widthedge of each of the preliminary cutting forms is substantially parallelto the width edge of a corresponding portion in which the preliminarycutting forms are inserted. The medium also includes code for causing acomputer to remove any of the preliminary cutting forms not having thewidth edge substantially parallel to the width edge of the correspondingmetal wire portion. The medium also has code for causing a computer todefine as final cutting forms the preliminary cutting forms having widthedges determined as substantially parallel to the width edge of thecorresponding metal wire portion.

A computer system includes a memory and a processor that identify ametal wire in the integrated circuit layout to receive the cuttingforms. The metal wire has at least one metal wire portion having aportion length edge and a portion width edge. The memory and processorinsert with a first orientation of preliminary cutting forms within theat least one portion of the metal wire, each of preliminary cuttingforms having a width edge and a length edge longer than the width edge.The memory and processor determine if the width edge of each of thepreliminary cutting forms is substantially parallel to the width edge ofthe corresponding portion in which the preliminary cutting forms areinserted. The memory and processor remove any of the preliminary cuttingforms not having the width edge substantially parallel to the portionwidth edge of the corresponding metal wire portion; and define as finalcutting forms the preliminary cutting forms having width edgesdetermined as substantially parallel to the width edge of thecorresponding metal wire portion.

In another aspect, a system generates a cutting form layout includingcutting forms for deleting metal along a current flow direction in anintegrated circuit layout. The system includes means for identifying ametal wire in the integrated circuit layout to receive the cuttingforms. The metal wire has at least one metal wire portion having alength edge and width edge. The system also has means for inserting witha first orientation preliminary cutting forms within the at least oneportion of the metal wire. Each of the preliminary cutting forms has awidth edge, and a length edge longer than the width edge. The systemfurther includes means for determining if the width edge of each of thepreliminary cutting forms is substantially parallel to a width edge of acorresponding portion in which the preliminary cutting forms areinserted. The system also has means for removing any of the preliminarycutting forms not having a width edge substantially parallel to thewidth edge of the corresponding metal wire portion. The system alsoincludes means for defining as final cutting forms the preliminarycutting forms having width edges determined as substantially parallel tothe width edge of the corresponding metal wire portion.

The foregoing has outlined rather broadly the features and technicaladvantages of the present disclosure in order that the detaileddescription of embodiments of the disclosure that follows may be betterunderstood. Additional features and advantages of the disclosure will bedescribed hereinafter which form the subject of the claims of thedisclosure. It should be appreciated by those skilled in the art thatthe conception and specific embodiments disclosed may be readilyutilized as a basis for modifying or designing other structures forcarrying out the same purposes of the present disclosure. It should alsobe realized by those skilled in the art that such equivalentconstructions do not depart from the spirit and scope of the disclosureas set forth in the appended claims. The novel features which arebelieved to be characteristic of the disclosure, both as to itsorganization and method of operation, together with further objects andadvantages will be better understood from the following description whenconsidered in connection with the accompanying figures. It is to beexpressly understood, however, that each of the figures is provided forthe purpose of illustration and description only and is not intended asa definition of the limits of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an exemplary wireless communication system in which anembodiment of the disclosure may be advantageously employed.

FIG. 2 is a flow diagram illustrating a method for generating cuttingforms along the current flow direction in a design layout according toan embodiment of the disclosure.

FIGS. 3-9 illustrate various stages of a method of placing cutting formsaccording to an embodiment of the disclosure shown in FIG. 2.

DETAILED DESCRIPTION

A method is disclosed to generate cutting forms within metalinterconnect wires, wherein the cutting forms are arranged in parallelwith the current flow direction. In an embodiment, a methodology placesthe long dimension of a cutting form parallel with the length edge ofthe metal wire portion. This is equivalent to aligning the smallerdimensioned width edge of the cutting form to be substantially parallelto a width dimension of the metal wire. In one embodiment, the metalwire portion in which the cutting form is placed may be represented bypiece-wise rectangles, where the larger dimension is in the direction ofcurrent flow. The width dimension of the piece-wise rectangle of themetal wire portion is an edge that may be referred to as the metal wireportion width edge.

In an embodiment of the disclosed method, the width edge of a cuttingform added to the metal wire portion of the layout and the width of themetal wire portion are identified and compared. Multiple cutting formsmay be placed throughout the entire metal wire layout and thenindividually evaluated. If the cutting form width edge is parallel tothe metal wire portion width edge, the cutting form is determined to bealigned in parallel with the electric current flow direction and isretained. Cutting forms not aligned in parallel with the electriccurrent flow direction are withdrawn. Then, alternative arrangements ofcutting forms (e.g., at ±45 degrees, ±90 degrees or another selectedangle to the original of the previously added cutting forms) may beinserted where cutting forms are not presently disposed, and the cuttingform width edge and the metal wire portion width edge direction areidentified and compared, as before. When the inserted cutting forms soplaced with a changed orientation in the piece-wise portion of the metalwire are aligned in parallel with the electric current flow directionand having the cutting form width edges being parallel to the metal wireportion width edge direction, they are retained. Other cutting forms notsatisfying the insertion criteria are again discarded.

The process is repeated until all cutting forms placed within all metalwire portions are arranged with the long dimension of the cutting formsparallel to the current flow directions in all portions of the metalwire. As the direction of the metal wire changes because of wire routingprocedures, the cutouts are continuously compared to the orientation ofthe piece-wise portions of the metal wire to establish the direction ofadditional cutting forms. The method may be applied to metal wires laidout in a variety of patterns.

The inserted cutting forms may be placed in a staggered pattern. Forexample, columns of cutting forms may be inserted in a straight portionof the metal wire with adjacent columns shifted relative to each otheralong the direction of current flow. This may improve the uniformity ofcoupled parasitic capacitance between adjacent layers of metal wiresthat may cross or overlap.

FIG. 1 shows an exemplary wireless communication system 100 in which anembodiment of the disclosure may be advantageously employed. Forpurposes of illustration, FIG. 1 shows three remote units 120, 130, and150 and two base stations 140. It will be recognized that typicalwireless communication systems may have many more remote units and basestations. Remote units 120, 130, and 150 include powered integratedcircuit devices 125A, 125B, and 125C, respectively, which utilizeembodiments of the disclosure as discussed further below. FIG. 1 showsforward link signals 180 from the base stations 140 and the remote units120, 130, and 150 and reverse link signals 190 from the remote units120, 130, and 150 to base stations 140.

In FIG. 1, a remote unit 120 is shown as a mobile telephone, remote unit130 is shown as a portable computer, and the remote unit 150 is shown asa fixed location remote unit in a wireless local loop system. Forexample, the remote units may be cell phones, hand-held personalcommunication systems (PCS) units, portable data units such as personaldata assistants, or fixed location data units such as meter readingequipment. Although FIG. 1 illustrates remote units according toembodiments taught in the disclosure, the disclosure is not limited tothese exemplary illustrated units. Embodiments of the disclosure may besuitably employed in any device which includes active integratedcircuitry including metal interconnect wires, for example, in powerdistribution.

FIG. 2 is a flow diagram illustrating one embodiment of a method forgenerating cutting forms along the current flow direction in a circuitdesign layout. FIGS. 3-9 illustrate various stages of placing cuttingforms according to the method of FIG. 2. Referring to FIGS. 2 and 3, themethod 200 begins with inputting data to specify a layout (Block 201)for one or more portions of a metal wire 301 (e.g., metal wire portions301 a, 301 b, etc.). In this example, a portion of the metal wire 301may be the rectangular metal wire portion 301 a. Layout data isevaluated to identify and select which wires in the layout are wideenough to merit insertion of cutting forms. (Block 202). For example, ifa wire has a width less than a selected range of wire widths, e.g., lessthan about 10 μm, it may not have cutting forms inserted. Those wireshaving a width in the selected range have cutting forms inserted. Theidentification of the length of the portion 301 a may be determined inthe evaluation by the length being greater than the width of the portion301 a. A width edge orientation WE and a length edge orientation LE maybe defined on the basis of the identified width and length of the metalwire portion (e.g., 301 a).

When a given segment 301 a is determined to be wide enough to includecutting forms, preliminary first cutting forms 302 of a selected size(e.g., rectangles having a first cutting form length dimension l_(cf)and width dimension w_(cf)) are inserted throughout the metal wire 301,aligned in one orientation (Block 203). While the preliminary cuttingforms 302 may be placed throughout all portions of the metal wire, thepreliminary cutting forms 302 will be evaluated according to criteriadetermined by one portion, e.g., portion 301 a. In other words, theevaluation is performed portion by portion.

In one embodiment the cutting forms 302 are placed in a staggeredpattern. Furthermore, the staggered pattern of the placement of thecutting forms 302 may be random or periodic, provided the cutting forms302 do not overlap. In one embodiment, the cutting forms 302 may beplaced in a uniform rectangular array pattern.

The orientation may be arbitrarily chosen. In one embodiment, thecutting forms 302 are arranged at angles of zero degrees, ±45 degrees,±90 degrees and ±135 degrees with respect to the layout horizontal(i.e., x) direction. Of course other angles may also be specified.

A selected length dimension l_(cf) and a selected width dimension w_(cf)of the cutting forms 302 may be arbitrarily chosen, wherein thedimension l_(cf) is customarily greater than the width dimension w_(cf).The cutting forms 302 may uniformly have the same dimensions, l_(cf) andw_(cf), or these dimensions may be varied from one cutting formplacement to another, e.g., from one portion to another portion of themetal wire 301.

In order to reduce calculations, in one embodiment it is determinedwhich cutting forms 301 are arranged in a column with other cuttingforms. Thus, the calculation can be performed for the entire column ofpreliminary cutting forms at one time. Referring to FIG. 2 and FIG. 4,an example of the procedure will now be described. Preliminary cuttingforms 302 a and 302 b are considered to be in the same column.Preliminary cutting forms 302 c and 302 d are considered to be inanother column. Preliminary cutting form 302 e defines a column nothaving any other preliminary cutting forms.

Based on the inserted preliminary cutting forms 302 a,b,c,d, temporarycolumnar cutting forms 303 may be defined in the following manner: Thetemporary columnar cutting forms 303 are shaped by having the lengthdimension l_(cf) elongated to a length l′_(cf). Additionally, the widthdimension w_(cf) of the preliminary cutting forms 302 a,b,c,d arereduced to w′_(cf) by a specified amount (e.g., 5 nm). The reduced widthdimension w′_(cf) of the temporary columnar cutting forms 303 ensuresthe temporary columnar cutting forms 303 do not overlap a preliminarycutting form 302 in an adjacent column.

Next it is evaluated whether the preliminary cutting forms 302 areoriented parallel to the direction of current flow. If there aremultiple preliminary cutting forms 302 within a single column, theevaluation can occur with respect to the entire column. In this case,the temporary columnar cutting forms' length l′_(cf) may be extendeduntil it touches an edge of the metal wire segment 301 a, as shown inFIG. 5. Similarly, in columns having only a single preliminary cuttingform 302 (e.g., 302 e), the single preliminary cutting forms 302 areextended until touching an edge of the wire metal segment 301 a, asshown in FIG. 5 (Block 204). These extended temporary columnar cuttingforms and the extended preliminary cutting forms will be collectivelyreferred to as temporary elongated cutting forms 503.

The orientation of the width edge of each of the newly formed temporaryelongated cutting forms 503 is identified and compared to the width edgeorientation WE of each portion of the metal wire 301 (e.g., 301 a, 301b, etc.) (Block 205). The comparison determines whether the width edgesof each of the temporary elongated cutting forms 503 are substantiallyparallel to the width edge orientation WE of each portion of the metalwire 301. Temporary elongated cutting forms 503 having width edgesw′_(cf) substantially parallel to the orientation WE of the metal wiresegment 301 a are identified in Block 205. When this criterion is met byany of the temporary elongated cutting forms 503, this indicates thatthe preliminary cutting forms corresponding to the temporary elongatedcutting forms 503 are substantially aligned in the current flowdirection, i.e., parallel to the length orientation LE of the portion301 a. Temporary elongated cutting forms 503 not aligned in the currentflow direction by having width edges (of dimension w′_(cf)) notsubstantially parallel to the width edge orientation WE of the portion301 a of the metal wire 301 are determined not to be parallel to thedirection of current flow in that portion 301 a (Block 207).

When the temporary elongated cutting forms 503 do meet the criterion ofBlock 205, the preliminary cutting forms 302, corresponding to thetemporary elongated cutting forms 303 are retained (Block 206). Thepreliminary cutting forms 302 subsumed by the temporary elongatedcutting forms 503 not meeting the criteria of Block 205 are withdrawnfrom placement (Block 207). As seen in FIG. 6, in the illustratedexample, the preliminary cutting forms 302 are withdrawn from theportion 301 b of the metal wire 301. All of the temporary elongatedcutting forms 503 are also withdrawn, as they serve the purposesubstantially to identify which preliminary cutting forms 302 are to beretained (FIG. 7).

In those portions of the metal wire 301 from which the preliminarycutting forms 302 have been removed (the portion 301 b in this example),new preliminary cutting forms 802 of a selected size are inserted with adifferent orientation from the previous preliminary cutting forms 302(Block 208) as illustrated in FIG. 8. In an embodiment, the orientationof the new preliminary cutting forms 802 may be, for example, at anangle of ±45 degree, ±90 degrees, or another orientation that maycorrespond to layout orientations and/or current flow directions for thevarious portions of the metal wire 301.

After inserting the new preliminary cutting forms 802 (in Block 208),the method 200 then returns to Block 204, repeating Blocks 204, 205,206, 207 and 208 until all portions of the metal wire have preliminarycutting forms 302, 802 satisfactorily placed with the long dimensionparallel to the direction of current flow (FIG. 9). Thus, when a portionof the metal wire 301 has retained preliminary cutting forms (302, 802,etc.) placed with the length dimension parallel to the currentdirection, it is determined whether all metal wire portions have cuttingforms inserted properly (Decision Block 209). If the result of DecisionBlock 209 is that insertion of cutting forms in all portions of themetal wire 301 is not complete (Block 209: No), the method 200 returnsto Block 208 to place more preliminary cutting forms 802 in vacantportions of the metal wire 301.

If all portions of the metal wire 301 have preliminary cutting forms(e.g., 302, 802,) placed and properly aligned (Block 209: YES), then thepreliminary cutting forms are defined as final cutting forms and apreliminary cutting form layout is output, with the final cutting formshaving the dimensions and orientations of the preliminary cutting forms302, 802 (Block 210).

The preliminary cutting form output may then be inspected to determineif additional adjustments are appropriate (Block 211), for example whena placement conflict arises. Final adjustments may be provided by anautomated procedure in which various specified conditions may be met, orthe final adjustments may be in response to visual inspection accordingto various specified conditions. A final placement of cutting forms isprovided after adjustment (Block 212).

In the event that a circuit design includes multiple metallized layers,wherein each layer includes metal wires, the method 200 may be appliedfor each layer. In multi-layer metallizations including metal wires inthe multiple layers, dielectric interlayers may electrically insulatetwo adjacent metallization layers that cross or overlap. In the casewhere the metal wires in two adjacent metallization layers remaininsulated, the cutting forms may be staggered as described above toprovide a substantially uniform inter-layer capacitance between the twometal wires. In one embodiment, where the metal wires in two adjacentmetallization layers are interconnected by metal-filled vias through theinterlayer dielectric, the method 200 is not applied in the overlappinginterconnect region, so the placement of cutting forms does notinterfere with the vias.

It will be appreciated that the method set forth automates the processof placing cutting forms in a metal wire, with the benefit of reducingmetallization dishing effects (i.e., that reduce the thickness in thecenter portion of metal wire traces) by breaking up extended areas ofmetallization. Additionally, where such metal wires serve to carry highcurrent densities for purposes of supplying power to circuitry, thecutting forms in metal wire traces may also be placed (e.g., staggered)to limit growth of electromigration effects, which otherwise contributeto increased wire resistance, causing localized heating and failure overtime.

The methodologies described herein may be implemented by various meansdepending upon the application. For example, these methodologies may beimplemented in hardware, firmware, software, or a combination thereof.For a hardware implementation, the processing units may be implementedwithin one or more application specific integrated circuits (ASICs),digital signal processors (DSPs), digital signal processing devices(DSPDs), programmable logic devices (PLDs), field programmable gatearrays (FPGAs), processors, controllers, micro-controllers,microprocessors, electronic devices, or other electronic units designedto perform the functions described herein, or a combination thereof.

For a firmware and/or software implementation, the methodologies may beimplemented with modules (e.g., procedures, functions, and so on) thatperform the functions described herein. Any machine readable mediumtangibly embodying instructions may be used in implementing themethodologies described herein. For example, software codes may bestored in a memory, for example the memory of a mobile station, andexecuted by a processor, for example the microprocessor of a modem.Memory may be implemented within the processor or external to theprocessor. As used herein the term “memory” refers to any type of longterm, short term, volatile, nonvolatile, or other memory and is not tobe limited to any particular type of memory or number of memories, ortype of media upon which memory is stored.

Although the present disclosure and its advantages have been describedin detail, it should be understood that various changes, substitutionsand alterations can be made herein without departing from the spirit andscope of the disclosure as defined by the appended claims. For example,although the preceding description was with respect to inserting cuttingforms in wide metal wires, the disclosed methods and structures may beused whenever it is desirable to design a layout with a preferredorientation for selected features. Moreover, the scope of the presentapplication is not intended to be limited to the particular embodimentsof the process, machine, manufacture, composition of matter, means,methods and steps described in the specification. As one of ordinaryskill in the art will readily appreciate from the present disclosure,processes, machines, manufacture, compositions of matter, means,methods, or steps, presently existing or later to be developed thatperform substantially the same function or achieve substantially thesame result as the corresponding embodiments described herein may beutilized according to the present disclosure. Accordingly, the appendedclaims are intended to include within their scope such processes,machines, manufacture, compositions of matter, means, methods, or steps.

1. A method for generating a cutting form layout including cutting formsfor deleting metal along a current flow direction in an integratedcircuit layout, comprising: identifying a metal wire in the integratedcircuit layout to receive the cutting forms, the metal wire comprisingat least one metal wire portion having a portion length edge and portionwidth edge; inserting with a first orientation a first plurality ofpreliminary cutting forms within the at least one portion of the metalwire, each of the first plurality of preliminary cutting forms having awidth edge, and a length edge longer than the width edge; determining ifthe width edge of each of the first plurality of preliminary cuttingforms is substantially parallel to a width edge of a correspondingportion in which the first plurality of preliminary cutting forms areinserted; removing any of the first plurality of preliminary cuttingforms not having a width edge substantially parallel to the width edgeof the corresponding metal wire portion; and defining as final cuttingforms the first plurality of preliminary cutting forms having widthedges determined as substantially parallel to the width edge of thecorresponding metal wire portion.
 2. The method of claim 1, furthercomprising: inserting within the metal wire at a portion where theplurality of preliminary cutting forms have been removed a secondplurality of preliminary cutting forms having a second orientation, alength and a width; determining if the width edge of each of the secondplurality of preliminary cutting forms is substantially parallel to awidth edge of a corresponding portion in which the second plurality ofpreliminary cutting forms are inserted; removing any of the secondplurality of preliminary cutting forms not having a width edgesubstantially parallel to the width edge of the corresponding metal wireportion; and defining as final cutting forms the second plurality ofpreliminary cutting forms having width edges determined as substantiallyparallel to the width edge of the corresponding metal wire portion. 3.The method of claim 1, in which the identifying further comprises:identifying the metal wire portion to receive inserted cutting forms bycomparing a metal wire width to a selected width value.
 4. The method ofclaim 1, further comprising forming a plurality of elongated temporarycutting forms by extending the length of some of the first plurality ofpreliminary cutting forms along a length direction of the firstpreliminary cutting forms so each elongated temporary cutting form atleast partially overlaps with at least one other of the firstpreliminary cutting forms and/or touches an edge of the correspondingmetal wire portion.
 5. The method of claim 4, further comprisingreducing the width of the first plurality of the preliminary cuttingforms.
 6. The method of claim 2, further comprising forming a pluralityof elongated temporary cutting forms by extending the length of some ofthe second plurality of preliminary cutting forms along a direction ofthe metal length so each elongated temporary cutting form at leastpartially overlaps with at least one other of the second preliminarycutting forms and/or touches an edge of the corresponding metal wireportion.
 7. The method of claim 6, further comprising reducing the widthof the second plurality of the preliminary cutting forms.
 8. The methodof claim 1, further comprising outputting a location and orientationassociated with the final cutting forms.
 9. The method of claim 8,further comprising: adjusting the layout of the final cutting formsaccording to selected rules; and outputting a final layout.
 10. Acomputer program product for generating cutting forms for deleting metalalong a current flow direction in an integrated circuit layout,comprising: a computer-readable medium comprising: code for causing acomputer to identify a metal wire in the integrated circuit layout toreceive the cutting forms, the metal wire comprising at least one metalwire portion having a portion length edge and portion width edge; codefor causing a computer to insert with a first orientation a firstplurality of preliminary cutting forms within the at least one portionof the metal wire, each of the first plurality of preliminary cuttingforms having a width edge, and a length edge longer than the width edge;code for causing a computer to determine if the width edge of each ofthe plurality of preliminary cutting forms is substantially parallel toa width edge of a corresponding portion in which the first plurality ofpreliminary cutting forms are inserted; code for causing a computer toremove any of the first plurality of preliminary cutting forms nothaving a width edge substantially parallel to the width edge of thecorresponding metal wire portion; and code for causing a computer todefine as final cutting forms the first plurality of preliminary cuttingforms having width edges determined as substantially parallel to thewidth edge of the corresponding metal wire portion.
 11. Thecomputer-readable medium of claim 10, further comprising: code forcausing a computer to insert within the metal wire at a portion wherethe plurality of preliminary cutting forms have been removed a secondplurality of preliminary cutting forms having a second orientation, alength and a width; code for causing a computer to determine if thewidth edge of each of the second plurality of preliminary cutting formsis substantially parallel to a width edge of a corresponding portion inwhich the second plurality of preliminary cutting forms are inserted;code for causing a computer to remove any of the second plurality ofpreliminary cutting forms not having a width edge substantially parallelto the width edge of the corresponding metal wire portion; and code forcausing a computer to define as final cutting forms the second pluralityof preliminary cutting forms having width edges determined assubstantially parallel to the width edge of the corresponding metal wireportion.
 12. The computer-readable medium of claim 10, furthercomprising: code for causing a computer to identify the metal wireportion to receive inserted cutting forms by comparing a metal wirewidth to a selected width value.
 13. The computer-readable medium ofclaim 12, further comprising code for causing a computer to form aplurality of elongated temporary cutting forms by extending the lengthof some of the first plurality of preliminary cutting forms along alength direction of the first preliminary cutting forms so eachelongated temporary cutting form at least partially overlaps with atleast one other of the first preliminary cutting forms and/or touches anedge of the corresponding metal wire portion.
 14. The computer-readablemedium of claim 13, further comprising code for causing a computer toreduce the width of the first plurality of the preliminary cuttingforms.
 15. The computer-readable medium of claim 11, further comprisingcode for causing a computer to form a plurality of elongated temporarycutting forms by extending the length of some of the second plurality ofpreliminary cutting forms along a direction of the metal length so eachelongated temporary cutting form at least partially overlaps with atleast one other of the second preliminary cutting forms and/or touchesan edge of the corresponding metal wire portion.
 16. Thecomputer-readable medium of claim 15, further comprising code forcausing a computer to reduce the width of the second plurality of thepreliminary cutting forms.
 17. The computer-readable medium of claim 10,further comprising code for causing a computer to output a location andorientation associated with the final cutting forms.
 18. Thecomputer-readable medium of claim 17, further comprising code forcausing a computer to adjust the layout of the final cutting formsaccording to selected rules; and outputting a final layout.
 19. Acomputer system, comprising: a memory and a processor that: identify ametal wire in the integrated circuit layout to receive the cuttingforms, the metal wire comprising at least one metal wire portion havinga portion length edge and portion width edge; insert with a firstorientation a first plurality of preliminary cutting forms within the atleast one portion of the metal wire, each of the first plurality ofpreliminary cutting forms having a width edge, and a length edge longerthan the width edge; determine if the width edge of each of the firstplurality of preliminary cutting forms is substantially parallel to awidth edge of a corresponding portion in which the first plurality ofpreliminary cutting forms are inserted; remove any of the firstplurality of preliminary cutting forms not having a width edgesubstantially parallel to the width edge of the corresponding metal wireportion; and define as final cutting forms the first plurality ofpreliminary cutting forms having width edges determined as substantiallyparallel to the width edge of the corresponding metal wire portion. 20.The system of claim 19, in which the memory and processor identify themetal wire portion to receive inserted cutting forms by comparing ametal wire width to a selected width value.
 21. The system of claim 19,in which the memory and processor insert within the metal wire at aportion where the first plurality of preliminary cutting forms have beenremoved a second plurality of preliminary cutting forms having a secondorientation, a length and a width; determine whether second plurality ofpreliminary cutting forms are substantially parallel to a width edge ofa corresponding portion in which the second plurality of preliminarycutting forms are inserted; remove any of the second plurality ofpreliminary cutting forms not having a width edge substantially parallelto the width edge of the corresponding metal wire portion; and define asfinal cutting forms the second plurality of preliminary cutting formshaving width edges determined as substantially parallel to the widthedge of the corresponding metal wire portion.
 22. The system of claim19, in which the memory and processor adjust the layout of the finalcutting forms according to selected rules and output a final layout. 23.A system for generating a cutting form layout including cutting formsfor deleting metal along a current flow direction in an integratedcircuit layout, comprising: means for identifying a metal wire in theintegrated circuit layout to receive the cutting forms, the metal wirecomprising at least one metal wire portion having a portion length edgeand portion width edge; means for inserting with a first orientation aplurality of preliminary cutting forms within the at least one portionof the metal wire, each of the plurality of preliminary cutting formshaving a width edge, and a length edge longer than the width edge; meansfor determining if the width edge of each of the plurality ofpreliminary cutting forms is substantially parallel to a width edge of acorresponding portion in which the plurality of preliminary cuttingforms are inserted; means for removing any of the plurality ofpreliminary cutting forms not having a width edge substantially parallelto the width edge of the corresponding metal wire portion; and means fordefining as final cutting forms the plurality of preliminary cuttingforms having width edges determined as substantially parallel to thewidth edge of the corresponding metal wire portion.